Power manager

ABSTRACT

An improved power manager includes a power bus ( 410 ) and multiple device ports ( 1 - 5 ), with at least one device port configured as a universal port ( 3  and  4 ) to be selectively connected to the power bus over an input power channel that includes an input power converter ( 510 ) or over a output or universal power channel ( 412, 416 ) that includes an output power converter ( 440, 442 ). The universal power channel ( 412 ) allows the input port ( 4 ) to be selected as an output power channel instead of an input power channel (i.e. operated as a universal port) for outputting power to device port ( 4 ) over power converter ( 440 ). The improved power manager ( 500 ) includes operating modes for altering an operating voltage of the power bus ( 505 ), to minimize overall power conversion losses due to DC to DC power conversions used to connect non-bus voltage compatible power devices to the power bus.

1 CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application No. 61/807,028, filed Apr. 1, 2013, which is incorporated herein by reference.

2 BACKGROUND OF THE INVENTION

2.1 Field of the Invention

The exemplary, illustrative, technology herein relates to power manager systems suitable for operably connecting one or more power sources and one or more power loads to a power bus and distributing power from the power sources to the power loads over the power bus. The improved power manager includes at least one universal port that can be operated as an input port to receive input power from a power source and that can also be operated as an output port to deliver output power to a power load. Additionally the improved power manager includes system and operating method improvements provided to reduce power loss stemming from DC to DC power conversions.

2.2 The Related Art

Referring to FIGS. 1 and 2, a conventional power manager (100, 200) includes a Direct Current (DC) power bus (105) and six power ports (110, 130) operably connectable with the power bus. Up to six external power devices (115, 120) can be connected, one to each of the six device ports (110), and all six external power devices can be operably connected to the power bus (105) simultaneously. In one particularly relevant embodiment disclosed in U.S. Pat. No. 8,633,619 to Robinson et al. entitled Power managers and method for operating power managers, issued on Jan. 21, 2014; a power manager is disclosed that includes six device ports. The power manager system disclosed by Robinson et al. is shown schematically in FIGS. 1 and 2. In FIG. 1, a power manager (100) includes six device ports with two input device ports (130) and four output device ports (110). When all the device ports are connected to external power devices each device port (110, 130) is connected to an input power or energy source (115) or to a power load (120).

Each device port is operably connectable to a power bus (105) by operating one or more controllable switches. In an initial state each controllable switch is open (shorted) to disconnect the device port from the power bus. An electronic controller (125, 205) operates the controllable switches according to an energy management schema program or firmware running on the electronic controller. The electronic controller also communicates with each external device (115, 210) or with a smart cable associated with the external device to determine its operating voltage range and other power characteristics. The electronic controller continuously monitors external devices connected to the device ports and continuously evaluates if each connected external power device is a power source or a power load and further determines whether the external power device can be connected to the power bus (105) or not. In the event that the electronic controller determines that the connected external device is not compatible with connecting to the power bus the device is not connected. In the event that the electronic controller determines that an external device already connected to the power bus is no longer compatible with connecting to the power bus the device is disconnected by actuating a controllable switch.

The power manager (100, 200) is configured as a Direct Current (DC) device suitable for use with DC power sources and DC power loads. The conventional power bus (105) operates at a substantially fixed DC voltage. While the fixed bus DC voltage may fluctuate as power loads and power sources are connected to or disconnected from the power bus (105) the power bus voltage is substantially maintained within a small voltage range, e.g. 10-14 volts or the like, referred to herein as a “bus-compatible voltage.”

When an external power device (115, 120) is determined to be operable at a bus-compatible voltage the external power device (115, 120) is preferably directly connected to the power bus without any power conversion. Thus power sources and power loads that can operate at the bus-compatible voltage can be directly connected to the power bus (105) over any one of the device ports (110) or (130) without the need for a voltage conversion. This is demonstrated in FIG. 2 which shows a schematic representation of a pair of input device ports (130 a) and (130 b) each connectable to the power bus (105) over two different connection paths and a pair of output device port (110 a) and (110 b) each connectable to the power bus (105) over two different connection paths. As shown, each input device port (130 a, 130 b) includes a first power channel (1080) that extends between the device port (130 a) and the power bus (105) and another first power channel (1085) that extends between the device port (130 b) and the power bus (105). As also shown each first power channel (1080, 1085) includes a first controllable switch (1040) disposed between port (130 a) and the power bus and first controllable switch (1030) disposed between port (130 b) and the power bus. Similarly each output port (110 a, 110 b) also includes a first power channel (1090, 1095) and a first controllable switch (1055) disposed between the output port (110 a) and the power bus (105). Thus all six device ports include a first power channel for directly connecting an external device connected to the device port to the power bus when the first controllable switch is closed.

In operation the first controllable switch is opened preventing the external device from connecting with the power bus (105). The electronic controller (125) communicates with each external power source (115 a, 115 b) and with each external power load (120 a, 120 b) to determine operating voltages of each externally connected power device. If any of the connected external devices are operable at the bus compatible voltage the electronic controller (125) can actuate (close) the relevant first controllable switching elements (1030, 1040, 1055, 1060) to directly connect all of the external devices that can operate at the bus voltage to the power bus if other conditions of the energy management schema justify the connection. Moreover in the case where a power source or a power load is operable at the bus compatible voltage power sources (115 a, 115 b) and the power loads (110 a, 110 b) are interchangeable between the input device ports (130 a, 130 b) and the output ports (110 a, 110 b). More generally every device port (110) can be used as in input device port or an output device port when the connected external device is operable at the bus-compatible voltage.

Alternately when a connected external device is not operable at the bus-compatible voltage it can be connected to the power bus over a DC to DC power converter when the power converter is configurable to perform a suitable voltage conversion. This is demonstrated in FIG. 2 wherein the two input device ports (130 a, 130 b) share a single input power converter (1065) and the two output device ports (110 a, 110 b) share a single output power converter (1070). Each power converter (1065) and (1070) is unidirectional such that the power converter (1065) can only make a power conversion on an input power signal received from a power source (115 a, 115 b) and the power converter (1070) can only make a power conversion on an output power signal received from the power bus (105).

The input ports (115 a, 115 b) share the input power converter (1065) over a second power channel (1075). The channel (1075) is accessed by the device port (130 a) by opening the switches (1040) and (1035) while closing the switch (1025) such that a power signal received through the input device port (130 a) flows over the second power channel (1075) and through the power converter (1065) to the power bus (105). The channel (1075) can also be access by the device port (130 b) by opening the switches (1030) and (1025) and closing the switch (1035) such that a power signal received through the input device port (130 b) flows over the second power channel (1075) and through the power converter (1065) to the power bus (105). Thus one of the two input power sources (115 a) and (115 b) can be connected to the power bus over the input power converter via the second power channel (1075), both of the two input power sources (115 a) and (115 b) can be connected to the power bus over the two first power channels (1080) and (1085) or one of the two input power sources (115 a) and (115 b) can be connected to the power bus over the input power converter via the second power channel (1075) while the other of the two input power sources (115 a) and (115 b) is connected to the power bus over the relative first channel (1080) or (1085).

Similarly the output ports (110 a, 110 b) share the output power converter (1070) over a second power channel (1097). The channel (1097) is accessed by the device port (110 a) by opening the switches (1045) and (1055) while closing the switch (1050) such that a power signal flowing from the power bus (105) to the output port (110 a) flows through the output power converter (1070) and over the second power channel (1095) to the power load (120 a). The channel (1075) can also be accessed by the device port (110 b) by opening the switches (1050) and (1060) and closing the switch (1045) such that a power signal flowing from the power bus (105) to the output port (110 b) flows through the output power converter (1070) and over the second power channel (1095) to the power load (120 b).

Thus one of the two power loads (120 a) and (120 b) can be connected to the power bus over the output power converter via the second power channel (1097), both of the two power loads (120 a) and (120 b) can be connected to the power bus over the two first power channels (1090) and (1095) or one of the two power loads (120 a) and (120 b) can be connected to the power bus over the output power converter via the second power channel (1095) while the other of the two power loads (120 a) and (120 b) is connected to the power bus over the relative first channel (1090) or (1095). While not shown in FIG. 2 the remaining pair of output device ports (totaling six ports) is configured like the output device ports (110 a) and (110 b). Thus all six device ports of the device (100) include a first power channel for directly connecting an external device connected to the device port to the power bus when the first controllable switch disposed along the first power channel is closed. Meanwhile at the two input device ports (130 a) and (130 b) share an input power converter and each pair of output device ports shares an output power converter.

2.2.1 Empty Input Device Ports not Utilized

Accordingly one problem with the device disclosed by Robinson et al. is that for a given pair of device ports only one of the device ports has access to a power converter. In the case of the input device ports (130 a, 130 b) the input power converter (1065) can operate with one power conversion setting, e.g. to step up or step down the input voltage to match the bus voltage. Thus if two input sources are available and each has a different non-bus compatible operating voltage, only one of the two input sources is usable and one of the input device ports is available. While the unused input port can be used as an output port for a power load that is bus voltage compatible there is no opportunity to use the empty input port for a non-bus compatible voltage device. The problem also extends to the output side. As a result one of the input ports is not usable. In the case of the output device ports (110 a, 110 b) and other pairs on the power manager, the output power converters (1065) can operate with one power conversion setting, e.g. to step up or step down the bus voltage to match the connected non-bus voltage compatible power load. Thus if two power loads are in need of power and each has a different non-bus compatible operating voltage, only one of the two power loads can be powered and one of the two output device ports associated with the output power converter is available. While the unused output port can be used as an output port for a power load that is bus voltage compatible there is no opportunity to use the empty output port for a non-bus compatible voltage device.

Thus one problem that arises with conventional power managers that do not include a power converter for each device ports is that not all the available device ports can be utilized to power loads that require a power conversion. In one example, the bus is powered by a single power source connected to one of the input device ports (130 a, 130 b) and there are more than four power loads that need power. In this example four power loads may be able to be powered at the four output ports (110) but one of the input ports (130) is empty. While the empty input port can be utilized to power a load with a bus compatible operating voltage there is a need to utilize the empty input port to power a load that needs a power conversion. More generally there is a need to utilize empty input and output device ports to power loads that require a power conversion.

2.2.2 Power Loss Resulting from Each Power Conversion

A further problem in the art relates to suffering power losses associated with each power conversion. As is well known, each power conversion (e.g. a buck/boost converter) has an associated power loss in proportion to the input and output voltage and the input and output current amplitude. The power loss for such a conversion for a defined set of input and output currents can be approximated by:

PLoss=Ls(|Vin−Vout|)  Equation 1

where the power loss PLoss is the power lost due to the voltage conversion for given input and output current amplitudes, Ls is a loss factor associated with the particular power converter or type of power converter, Vin is the input voltage, and Vout is the output voltage. Thus the power loss is directly proportional to the step up or step down voltage.

2.2.3 Fixed Bus Voltage Can Lead to Power Loss

When a power manager (e.g. 200) is operated with a fixed bus voltage, unnecessarily large step up and step down voltage conversions are sometimes performed, leading to unnecessary power loss. Moreover, as described above, operating a power manager with a fixed bus voltage can lead to empty device ports that are not usable to power loads. Since all the device ports of the device shown in FIG. 2 include a power channel to directly connect a power device to the power bus without a power conversion, allowing the bus voltage to match the voltage of at least some of the power devices connected to the power bus can help to avoid power conversions. Alternately reducing the step up or step down voltage at each converter can also reduce power conversion losses.

In a conventional operating mode, a fixed bus voltage ranges from 12-16 volts, but the user has a 30 volt power supply and a plurality of 30 volt power loads that need to be connected to the power manager. In this case, each 30 volt device requires a power conversion to connect to the power bus. When each device is power converted, power losses occur at each device port. Given that in many cases, power managers are used in remote locations to simultaneously power a plurality of power loads using limited input power resources, a power loss at every device port is not desirable. Thus, there is a need in the art for a power manager that can adapt its bus voltage according to the configuration of power devices connected to it to reduce power loss and maximize device port utilization.

3 SUMMARY OF THE INVENTION

In view of the problems associated with conventional methods and apparatus set forth above, it is an object of the present invention to improve device port utilization by making more device ports available to power additional non-bus voltage compatible power loads.

It is a further object of the invention to reduce power loss associated with power conversions by performing fewer power conversions.

It is a further object of the invention to reduce power loss when power conversions are performed by reducing the quantity |Vin−Vout| listed in Equation 1.

It is a still further object of the present invention to provide a power manager that operates at a plurality of different bus voltage operating points.

It is a still further object of the present invention to determine a bus voltage operating point that reduces power loss according to the operating voltages of connected power devices.

5 BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention will best be understood from a detailed description of the invention and example embodiments thereof selected for the purposes of illustration and shown in the accompanying drawings in which:

FIG. 1 illustrates a schematic diagram representing a conventional power manager having six device ports connected to a power bus with 2 device ports configured as input ports and four device ports configured as output ports.

FIG. 2 illustrates a schematic diagram representing a portion of a conventional power manager with two input ports sharing an input power converter and two output ports sharing and output power converter.

FIG. 3 illustrates a schematic diagram representing a first non-limiting exemplary embodiment of a power manager having an improved power channel layout according to the present invention.

FIG. 4 illustrates a schematic diagram representing a second non-limiting exemplary embodiment of a power manager having an improved power channel layout and control system according to the present invention.

FIG. 5 illustrates a schematic diagram representing a third non-limiting exemplary embodiment of an improved power manager having a variable voltage power bus according to one aspect of the present invention.

5 DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

5.1 Overview

5.1.1 Expanded Access to Power Converted Output

In exemplary, non-limiting, embodiments of the invention an improved power manager operating with a fixed bus voltage includes additional power channels and related control elements for routing power from an output power converter to a plurality of device ports, including to device ports associated with an input power converter. The additional power channels allow a user of the power manager to connect power loads to input device ports even when the power load connected to the input device port operates with a non-bus compatible voltage. In one example embodiment shown in FIG. 3, a single input device (115 b) is used to power three power loads (110 a, 110 b, 110 c) over a single output converter (3070), as illustrated by bold arrows, indicating flow of power from power source (115 b) to power loads (110 a, 110 b, 110 c). This in an improvement over conventional power manager (200) which is limited to powering only two power loads (110 a, 110 b) over a single power converter (1070).

In a further example shown in FIG. 4, a single input source connected to power manager (400) at device port (3) is used to power three power loads, power loads at ports (1, 2, and 6), over a single output power converter (440) by providing an additional power channel (414) and associated controllable switch (484). This is an improvement over conventional power managers which are limited to powering only two power loads over a single power converter. In further embodiments, additional power channels are provided to power more than three device ports through a single output power converter (440). Meanwhile each of the device ports of the improved systems (300) and (400) each includes a first power channel and first controllable switch provided to connect any bus compatible voltage power device connected to any device port to the power bus without passing over a power converter.

5.1.2 Bus Voltage Varied to Reduce Power Conversion Losses

In exemplary, non-limiting, embodiment of the invention an improved power manager (500), shown in FIG. 5, manages the device bus voltage according to the collective operating voltages of external power devices connected to the power bus. The power manager further includes an electronic controller and a communications interface module wherein the communications interface module connects the electronic controller to the each device port, to sensors measuring power conditions on the power bus and to other components of the power manager. The controller receives information regarding the external devices connected to the power manager and controls components of the power manager to set the bus voltage, to set power conversion parameters of the power converters, and to connect and disconnect device ports to and from the power bus according to an energy management schema. The controller is further configured to collect operating voltage parameters of each external power device connected to a device port and to calculate a bus voltage that minimizes power losses due to power conversions required by power converters to connect power devices to the power bus. The need for a power manager that reduces power losses due to power conversions is met by providing a power manager with a variable bus voltage wherein the bus voltage is set to a value that minimizes power losses due to conversion of input and output power to accommodate attached power sources and power loads.

These and other aspects and advantages will become apparent when the Description below is read in conjunction with the accompanying Drawings.

5.2 Item Number List (if Applicable)

The following item numbers are used throughout, unless specifically indicated otherwise.

# DESCRIPTION # DESCRIPTION 100 Power Manager 400 Power Manager 105 Power Bus 405 Electronic Controller 120 Device Port (Output Port) 403 Communication Interface 115 External Device Power Source 3 Device Port (Input Port/Universal Port) 110 External Device Power Load 4 Device Port (Input Port/Universal Port) 125 Electronic Controller 5 Device Port (Output Port) 130 Device Port (Input Port) 6 Device Port (Output Port) 1 Device Port (Output Port) 200 Power Manager 2 Device Port (Output Port) 205 Electronic Controller 410 Power Bus 210 Communication Interface 402 Direct Power Channel (Port 3) 1065 Input Power Converter 404 Direct Power Channel (Port 4) 1070 Output Power Converter 406 Direct Power Channel (Port 2) 1025 Switching Element 408 Direct Power Channel (Port 1) 1030 Switching Element 535 Direct Power Channel (Port 6) 1035 Switching Element 525 Direct Power Channel (Port 5) 1040 Switching Element 470 FET 1045 Switching Element 475 FET 1050 Switching Element 450 FET 1055 Switching Element 455 FET 1060 Switching Element 460 FET 1080 Non-Converted Power Channel 465 FET 1085 Non-Converted Power Channel 510 Input Power Converter 1090 Non-Converted Power Channel 532 Input Converter Power Channel 1095 Non-Converted Power Channel 503 FET 1075 First Conductive Channel 505 FET 1097 Second Conductive Channel 440 Output Power Converter 435 Output Converter Power Channel 300 Improved Power Manager 485 FET 305 Power Bus 480 FET 330 Universal Port 442 Output Power Converter 3080 Direct Power Channel 530 Output Converter Power Channel 3085 Direct Power Channel 495 FET 3090 Direct Power Channel 490 FET 3095 Direct Power Channel 412 Additional Power Channel (Port 4) 3065 Input Power Converter 482 FET 3075 Input Converter Power Channel 416 Additional Power Channel (Port 3) 3070 Output Power Converter 486 FET 3097 Output Converter Power Channel 310 Additional Power Channel 500 Power Manager 315 Controllable Switch 505 Power Bus 320 Controllable Switch 550 Electronic Controller 325 Controllable Switch 555 Communication Interface 560 Bus Sensor Module 510 Input Power Converter 515 Input Power Converter 520 Output Power Converter 525 Output Power Converter 503 Input Device Port 504 Output Device Port 530 Power Source 540 Power Load 5080 Non-Converter Power Channel 5085 Non-Converter Power Channel 5090 Non-Converter Power Channel 5095 Non-Converter Power Channel

5.3 Brief Description of the Invention

Referring to FIG. 3 an improved power manager (300) according to the present invention comprises a power bus (305) and a plurality of device ports (330, 120) connectable to the power bus over a plurality of independent power channels. Each power channel includes one or more control devices such as controllable switches (e.g., 1030, 1035, 1060, 325) and controllable DC to DC power converters (3065, 3070) in communication with an electronic controller (350). The electronic control may comprise a microprocessor or the like, and a separate or integrated data storage module (352) in communication with the electronic controller (350). In addition a communications interface (354) such as SMbus or the like extends to each device port to communicate with external power devices connected with the device ports. In addition the communications interface (354) further includes elements that interconnect operable and passive electronic devices within the power manager to the electronic controller (350) as required to operate switches, to operate the power converters (3065) and (3070), and to collect data from sensors and other electronic components.

Device ports (120 a, 120 b, 330 a, 330 b) are configured to interface with external power devices which may comprise power sources, power loads, or rechargeable batteries (energy sources). Rechargeable batteries may operate as an energy source when discharging to the power bus or as a power load when recharging or drawing power from the power bus. Throughout the specification when a power load is referenced it is understood that the term power load may encompass a rechargeable battery or other rechargeable energy storage device that is recharging or otherwise drawing power from the power bus (305). Similarly, the term power source is understood to encompass rechargeable batteries or other rechargeable power devices that are discharging power to the power bus (305). It is further noted that in a preferred embodiment each device port comprises a physical connector or plug suitable for connecting to an external power device over a wire or cable that is terminated by a connector or plug suitable for mating with the device port such that external devices are easily connected to or disconnected from device ports. It is further noted the preferred power manager (300) is a portable or more specifically man portable device and that the preferred power manager is a DC to DC device exchanging power only with other DC devices or devices that are converted to a suitable DC power signal. Additionally it is noted that the preferred device port includes a wire network channel such that the power managers can at least receive digital data from each external device connected to a device port over a wire network interface using a network protocol such as SMbus, RS232, USB and the like.

In one example embodiment, the power bus operates with a substantially fixed bus voltage although the embodiment of FIG. 3 is not limited to a fixed bus voltage device. The power manager includes control elements and programs stored on the data storage module (352) and operable on the electronic controller (350) for communicating with external power devices connected to device ports over the communication interface (354) to ascertain the device power characteristics, including a type and operating voltage range of each connected external power device. If the external power device is bus-voltage compatible (i.e. has an operating voltage that overlaps with the power bus voltage) the external device can be directly connected to the power bus over a direct power channel (e.g. 3080, 3085, 3090, 3095) by closing appropriate control switches (e.g. 1030, 1040, 1055, 1060) and opening appropriate controllable switches (e.g. 1025, 1035, 320, 325, 315 a and 315 b). Additionally, the electronic controller (350) operates energy management schema programs that select which external power devices to connect to the power bus (305) or to disconnect from the power bus (305) according to the overall operating configuration and operating mode of the power manager (300).

If the external power device does not have a bus-voltage compatible operating voltage the external device can be connected to the power bus over a power converter channel (e.g. 3075, 3097) that includes an input power converter (3065) for converting the input voltage of a power source to a bus compatible voltage converting or an output power converter (3070) for converting bus voltage to a suitable output voltage for powering a connected a power load. On the input side the input power converter (3065) can be configured to convert an input power signal by either stepping the input voltage up or stepping the input voltage down as required to match the bus voltage. In the present example, switch (1035) is closed and switches (1025) and (1030) are opened in order to direct input power from the power source (115 b) to the power bus over the input power converter channel (3070) which passes through the input power converter (3065). In another operating mode wherein the power source (115 b) has a bus compatible voltage the port (330 b) is connected directly to the power bus (305) without power conversion by opening the switches (1035) and (315 b) while closing the switch (1030).

The input and output power converters (3065) and (3070) are each controlled by the electronic controller (350) and are each operable to step the input voltage up or down as well as to modulate power amplitude. Additional each device is unidirectional with the input voltage of the input power converter (3065) coming from the input ports (330 a, 330 b) and the input voltage of the output power converter (3070) coming from the power bus (305). Generally the power converters operate to modulate power amplitude passing over the power converter between a substantially zero and a maximum available power amplitude. Moreover the power converters substantially prevent power from passing from the output side to the input side.

Two power sources (115 a) and (115 b) each having the same non-bus compatible voltage can be, connected one to each of the device ports (330 a) and (330 b), and power converted simultaneously by directing the input power from each of the device ports (330 a) and (330 b) over the power converter channel (3075) to the power converter (3065) as long as both external power sources require the same power conversion. In this example configuration, two power sources are connected to the power bus (305) over the power channel (3075) by opening and closing appropriate control switches and by configuring the power converter (3065) for the desired power conversion. In particular this is possible when switches (315 b), (315 a), (1030) and (1040) are open and switches (1035) and (1025) are closed. It is further noted that the power converter channel (3070) extends from the power bus (305) through the input power converter (3065) and branches onto tow paths to connect with each device port (330 a) and (330 b).

On the output side of the power bus the output power converter (3070) can be configured to power convert a power signal output from the power bus (305) to power an external power load connected to either one or both of the device ports (120 a or 120 b) over an output power converter channel (3097). In particular the output power converter channel (3097) extends from the power bus to the output power converter (3070) and then in two branches to each of the output device ports (120 b) and (120 a). In addition the power channel (3097) includes two controllable switches (325) and (320) which can be opened to disconnect a corresponding device port from the power bus or closed to connect a corresponding device port to the power bus over the output power converter. Accordingly, each of the external power loads (110 a) and (110 b) connected to the device port (120 a and 120 b) can be connected to the power bus over the output power converter (3070) when both loads (110 a and 110 b) have the same non-bus compatible operating voltage. In either case the devices (110 a and 110 b) are connected to the power bus (305) over the output power converter channel (3097) by opening and closing appropriate control switches and by configuring the output power converter (3070) for the desired power conversion.

As is the case on the input side, either or both of the output device ports (120 a) and (120 b) can be connected directly to the power bus (305) without power conversion. In the case of output device port (120 a) any power device that operates with a bus compatible voltage can be connected to the power bus over the power channel (3095) by opening switches (325) and (315 b) and closing switch (1060). In the case of output device port (120 b) any power device that operates with a bus compatible voltage can be connected to the power bus over the power channel (3090) by opening switches (320) and (315 a) and closing switch (1055).

In a further aspect of the present invention two additional power channels (310 a and 310 b) are disposed one each from the output of the power converter (3070) to two universal device ports (330 a and 330 b) respectively. Each power channel (310 a and 310 b) includes a controllable switch (315 a, 315 b) in communication with the electronic controller (350) for opening and closing each switch to connect or disconnect the appropriate power channel (310 a or 310 b) to deliver power to a power load connected to one of the universal device ports (330 a or 330 b) or both. In particular the present invention and specifically the power channels (310 a) and (310 b) allowed the input ports (330 a) and (330 b) to operate a universal port capable as being used as an input port for input power sources that require power conversion by an input power converter or as an output port for power loads that require power conversion by an output power converter.

In one operating example a power source (115 b) is connected to the power bus (305) over the input power converter (3065) through power channel (3075). Alternately the power source (115 b) can be directly connected to the power bus (305) over the power channel (3085) if the power source has bus compatible operating voltage. On the output side, the power load (110 a) is connected to the power bus (305) over the power converter (3070) by power channel (3097). Alternately or additionally the power load (110 b) is also connected to the power bus (305) over the power converter (3070) by the power channel (3097). In addition the power channel (3097) extends to power channel (310 a) when switch (315 a) is closed such that a power load (110 c) connected to the device port (330 a) is also connected to the power bus over the output power converter (3070). In alternative operating modes, one or both of the power devices (110 a, 110 b) can be directly connected to the power bus (305) without a power conversion over the power channels (3090 and 3095) respectively and in that case one or both of the power devices (110 a and 110 b) may comprise a power load or a power source or a rechargeable battery. In a further alternate operating mode the input power source (115 b) can be exchanged with a power load and connected to the power bus over the output power converter (3070) using the power channel (310 b) when switch (315 b) is closed.

In another exemplary operating mode, either one or both of device port (330 a) and device port (330 b) can be connected to bus (305) over power channels (310 a) and/or (310 b), respectively, while one, both, or neither of device ports (120 a, 120 b) are simultaneously connected to the power bus over output power converter (3070). In an exemplary operating mode one or both of device ports (120 a, 120 b), includes a connected power source having a bus compatible voltage and the respective device port is connected to the bus (305) over a non-converted power channel (3095, 3090). In such an operating configuration one or both of device ports (330 a, 330 b) may be connected to bus (305) through output power converter (3070) over channels (310 a, 310 b). Thus using a single power source having a bus compatible voltage connected to e.g. port (120 b) and directly connected to the power bus (305) over the channel (3095) up to three power loads having the same non-bus compatible operating voltage can be powered from the output power converter (3070).

The power channel (3097) extends from the output end of a power converter (3070) to each of the device ports (120 a and 120 b) and includes controllable switches (320 and 325) for connecting or disconnecting the devices (110 a and 110 b) as required. The additional power channels (310 a and 310 b) extend the power channel (3097) to the device ports (330 a and 330 b) and include additional controllable switches (315 a and 315 b) for connecting or disconnecting the device ports (330 a) and (330 b) to the output converter (3070) as required.

Thus the improved power manager (300) includes at least one universal port, (e.g. 330 a or 330 b), capable of operating as an input port or an output port with selectable input or output power conversion. Specifically, when a power device connected to the universal port (330 a) is determined to be a power source, the power source is either directly connected to the power bus over the power channel (3080) when no power conversion is required, or the power source is connected to the power bus over the input power converter (3065) using the power channel (3075), if the input power converter is available, i.e. not already in use or not able to make the desired power conversion. Conversely, when a power device connected to the universal port (330 a) is determined to be a power load, the power load is either directly connected to the power bus over the power channel (3080) when no power conversion is required, or the power load is connected to the power bus over the output converter (3070) if it is available, i.e. not already in use or not able to make the desired power conversion. In particular the electronic controller (350) checks the status of the output power converter (3070) to determine if it can be configured to connect a power load connected to the universal device port (330 a) to the power device. If the power converter is available (i.e. either not in use or not in use at a non-compatible power conversion setting), the power converter is configured with appropriate power conversion parameters to power he load connected to the universal port (330 a) and the switch (315 a) is closed to connect the power load (110 c) to the power bus over the power converter (3070). Meanwhile other switches that are opened or remain opened include (1040), (315 b) and possibly (320) and (325) depending on the external devices are connected to device ports (120 a) and (120 b).

In operation, all the control switches in the power manager (300) are initially opened to prevent current flow over any of the power channels. The electronic controller (350) then polls all of the device ports and determines if an external power device is connected and the power device type and power characteristics of each connected power device. Once the device types and characteristics are determined the energy management schema selects a system configuration which includes generating a list of external devices to connect to the power bus, determining the power conversion settings of each power converter, determining which power channel each device will be connected to the power bus over and determining which switches to open and close. Thereafter the electronic controller (350) periodically polls all of the device ports to update configuration information and the energy management schema operates to adjust the connected power device configuration according to program parameters. Additionally the electronic controller (350) initiates the polling process whenever a change in device configuration is detected, e.g. if an external device is connected or disconnected.

Typical example power and energy sources (115) include energy storage devices such as batteries; a grid power source (e.g. a wall outlet converted to DC power); mechanically driven power generators (such as fossil fuel engines, wind, water, or other mechanically driven power generators); and/or current generators such as photovoltaic and electrochemical devices. Example power loads (110) include any device powered by electricity, but usually include portable electronic devices that operate on a rechargeable DC battery or that operate on DC power received from the power manager. In some instances, an input power source may use an additional power conversion to become compatible with the power manager. For example, if an AC power grid is available (120 volts alternating at 60 Hz or 240 volts at 50 Hz), an additional external power converter is used to invert the AC current and step the AC voltage down from the grid voltage to a DC voltage that is either directly compatible with the power bus voltage range or that can be converted to the power bus voltage range using the DC to DC input power converter (3065). However, it is within the scope of the present invention to include a power converter within the power manager (300) that is configured to convert various AC power grid signals to a power signal that is compatible with power bus voltage range.

5.3.1 Power Manager with Six Ports

Referring now to FIG. 4, a power manager (400) comprises six device ports (1-6) operably connectable to a DC power bus (410). The power bus is operating at 15 volts DC with some moderate voltage variability around 15 volts (e.g. +/−3 volts) and is suitable for direct connection with external power devices having an operating voltage in the range of 15+/−3 volts. Each of the six device ports can be directly connected to the power bus (410) over a direct power channel (402, 404, 406, 408, 535, and 525) respectively by closing controllable switches or field-effect-transistor (FET), (470, 475, 450, 455, 460, and 465) disposed on each of the direct power channels between corresponding the device ports and the power bus. Each direct power channel extend from the device port to the power bus without power conversion and is used if the external device is operable at a bus compatible voltage e.g. 15+/−3 volts, i.e. when the external device is bus-voltage compatible. In the case where the external device is bus voltage compatible, the external device is operable as a power source or as a power load irrespective of whether the external device is connected to an input port or an output port. Power manager (400) includes an electronic controller (405) and associated communication interface (403), shown by dashed lines, electrically interfaced to each device port (1-6), to each power converter (510, 440, 442), and to each FET, (e.g. 503, 505, 480, 485, 482, 486, 490, 495). The communication interface (403) include a variety of network communication paths suitable for digital data communications, e.g. between the electronic controller (405) and external devices connected to device ports as well as other conductive paths or the like suitable for exchanging analog signals and or digital control signals e.g. with FET's voltage converters, sensors and other components of the power manager.

The power manager (400) includes two input ports (3, 4) associated with a single unidirectional input power converter (510). The input power converter (510) has an input power conversion range (step up or step down) of 4 to 34 volts. Either of the input ports (3, 4) is usable to connect an external power device to the power bus (410) over the power converter channel (532) that includes the power converter (510). Thus a non-bus voltage compatible power source connected to either one of the input ports (3) and (4) can be connected to the power bus (410) over the power converter (510) by closing either FET (503 or 505) when the power converter is operating at an appropriate step up or step down voltage. However the power converter (510) can only be used by one of the device ports (3) and (4) unless each device port is connected to a power source that requires the same power conversion setting to connect to the power bus. For example if substantially identical 24 volt power sources are connected to each of the device ports (3) and (4), each power source can be connected to the power bus with a 9 volt step down conversion and both devices can be simultaneously connected to the power bus over the power converter (510) by closing both FETs (503, 505) At the same time, each of the FET's (486, 470, 482, 475) is opened to disconnect the channels (416, 402, 404, 412) from the input device ports (3, 4).

The power manager (400) includes four output ports (1, 2) and (5, 6) each operably connectable to the power bus (410) and to external power devices suitable for connecting to the power bus. Output ports (1) and (2) are associated with a single unidirectional output power converter (440) disposed along an output power converter channel (435) which extends from the power bus to the output power converter (440) and branches to each of the ports (1, 2) over control switches (485) and (480). Output ports (5) and (6) are associated with a single unidirectional output power converter (442) disposed along an output power converter channel (530) which extends from the power bus to the out power converter (442) and branches to each of the ports (5, 6) over control switches (495) and (490). Each of the output power converters (440, 442) has an output power conversion range (step up or step down) of 10 to 24 volts. Either of the output ports (1, 2) is usable to connect an external power load to the power bus (410) over the output converter power channel (435) that includes the output power converter (440). It is noted that the converter power channel (435) is shared by the two ports (1, 2) and therefore can only be used for a single power conversion by one of the device ports (1, 2) unless both of the device ports can use the same power conversion. The output converter power channel (435) is accessed by port (1) by closing FET (485) and opening FET's (480), (455), (484) and (482).

Either of the output ports (5, 6) is usable to connect an external power load to the power bus over the output power converter channel (530) that includes the output power converter (442). It is noted that the output power converter channel (530) is shared by the two ports (5, 6) and therefore can only be used for a single power conversion by one of the device ports (5, 6) unless both device ports can use the same power conversion. The output power conversion channel (530) is accessed by port (6) by closing FET (490) and opening FET's (495), (460), (484) and (486).

The power manager (400) further includes a power channel (412) that extends from the output of power converter (440) by branching from converter power channel (435) to the input port (4) by branching to the device power channel (404). The power channel (412) allows a power load connected to input device port device port (4) to be connected to the power bus (410) over the output power converter (440). In addition the power manager (400) also includes a power channel (416) that extends from the output of power converter (442) by branching from converter power channel (530) to the input port (3) by branching to the device power channel (402). The power channel (416) allows a power load connected to input device port device port (3) to be connected to the power bus (410) over the output power converter (442). In addition, the power manager (400) also includes a power channel (414) that extends from the output of power converter (440) by branching from converter power channel (435) to both of the output ports (5) and (6) by branching to the device power channel (530). The power channel (414) allows a power load connected to either of the output device ports (5) or (6) to be connected to the power bus (410) over the output power converter (440). Alternately The power channel (416) can be used to connect a power load connected to either of the device ports (1) and (2) to the power bus over the output power converter (442).

In operation, the electronic controller (405) polls each device port to detect connected external power devices and the power device type and power characteristics of each connected power device. Once the device types and characteristics are determined the energy management schema selects a system configuration which includes generating a list of external devices to connect to the power bus, determining the power conversion settings of each power converter, determining which power channel each external power device will be connected to the power bus over and determining which switches to open and close. Thereafter the electronic controller (350) periodically polls all of the device ports to update configuration information and the energy management schema operates to adjust the connected power device configuration and power distribution according to program parameters. Additionally the electronic controller (405) initiates the polling process whenever a change in device configuration is detected, e.g. if an external device is connected or disconnected.

5.3.2 Power Manager Operating with a Variable Power Bus Voltage:

Referring now to FIG. 5, a power manager (500) is depicted schematically and includes a power bus (505) interfaced with a plurality of input power converters (510, 515) and a plurality of output power converters (520, 525). Each input power converter is associated with an input device port (503) for interfacing with an external power source (530) and each output power converter is associated with an output device port (504) for interfacing with an external power load (540). In alternate embodiments two or more ports may share a single power converter.

Each input device port (504) is connected to the power bus (505) over an input converter power channel (570) which includes a controllable switch (565) in communication with an electronic controller (550). The input converter channel (570) extends from the input device port (503 a) to the input power converter (515) over the controllable switch (565) and continues from the output of the power converter (515) to the power bus (505). Since the input converter is unidirectional power conversion is only performed to change input voltage. Specifically the voltage of an input power signal received from an external power source (530 a) connected to the input device port (503 a) can be stepped up or stepped down to match the operating voltage of the power bus. The switch (565) is operable by the electronic controller (550) to connect the external power source (530 a) to the power bus over the input power converter (515) by closing the switch (565) and to disconnect the input device port (503 a) by opening the switch (565). Other converter input power channels have the same configuration.

Each output device port (504) is connected to the power bus (505) over an output converter power channel (578) which includes a controllable switch (576) in communication with the electronic controller (550). The output converter channel (578) extends from the output device port (504 a) to the output power converter (520) over the controllable switch (576) and continues from the output of the power converter (520) to the power bus (505). Since the output converter is unidirectional power conversion is only performed to change output voltage. Specifically the voltage of a power bus signal received from the power bus (505) can be stepped up or stepped down to match the operating voltage of ab external power load (540 a) connected to the device port (504 a). The switch (576) is operable by the electronic controller (550) to connect the external power source (540 a) to the power bus over the output power converter (520) by closing the switch (576) and to disconnect the output device port (540 a) by opening the switch (576). Other converter output power channels have the same configuration.

Power manager (500) includes a non-converting power channel (5080, 5085, 5090, and 5095) associated with each device port (503 a, 503 b, 504 a, 504 b). The non-converting power channels are used to connect device ports and any external power sources (530 a, 530 b) and external power loads (540 a, 540 b) connected to device ports to the power bus. Each converted and non-converted power channel includes at least one controllable switching element (565, 566, 567, 568, 569, 572, 574, 578) that enables each power channel to be connected to or disconnected from the power bus. In additional embodiments, two or more input ports (503) or output ports (504) may share a single power converter as shown in FIGS. 3 and 4 above. In further embodiments, one or more input ports (503) may be configured as a universal port, i.e., selectively connectable to the power bus over an input power converter or an output power converter, for example with a configuration similar to that shown for ports (330) in FIG. 3.

An electronic controller (550) includes an associated data storage module and communication elements (555) suitable for exchanging command and control signals and data signals with internal devises such as the controllable switches (565, 566, 567, 568, 569, 572, 574, 578), the power converters (510, 515, 520, 525) the bus sensor module (560) and other internal modules as may be present. In addiction the communication elements include a communication interface that extends between the electronic controller (550) and each device port (503, 504). Moreover each device port is configured as a connector or terminator that includes both power and communication channels suitable for connecting with external power sources (530 a, 530 b), the power loads (540 a, 540 b). Preferably the communication elements (555) includes at least one network channel for data communication using a network protocol such as SMbus, USB, or the like for communicating with external devices. Otherwise the communication elements may comprise conductive paths, wires or the like, for exchanging analog signals between electronic components of the power manager, e.g. switches, sensors and power converters and the electronic controller (550).

According to the present invention, the electronic controller (550) includes various modules operating thereon, including a data storage module, for operating an energy management schema suitable for changing operating parameters of power manager elements e.g. to determine which external device(s) to connect to the power bus over which power channels and how power should be distributed as well as to alter an operating voltage of the power bus (505) in a manner that reduces power conversion loss. In one example embodiment, the electronic controller includes programs operating thereon for operating the power bus (505) at one of a plurality of different operating voltages, as well as for reconfiguring power converters and device port connections to the power bus in response in a change in power bus voltage.

In one example embodiment, the electronic controller (550) includes a look up table or the like stored in the memory module that lists a plurality of discreet bus voltage operating points, including a default bus voltage operating voltage. The preselected list of bus voltage operating points is chosen to match the operating range of the various power converters (510, 515, 520, and 525). Thus, if all of the power converters are capable of making power conversions over a voltage range of 5 to 50 volts, the list of potential power bus voltages may include operating points within the 5 to 50 volt range that tend to match standard source/load voltages such as 6, 12, 24, 30, and 42 volts. Alternately, the power manager (500) is configurable to operate at any bus voltage that practically allows power devices to connect to the power bus with or without a power conversion.

To select a power bus operating voltage, the electronic controller (550) polls each device port to gather power characteristics of all of the connected power devices and makes a determination as to which devices connected to the device ports require a power conversion to connect to the power bus based on the present power bus operating voltage. If no conversions are required, the power devices are connected to the power bus without power conversion over non-converted power channels (5080, 5085, 5090, and 5095). If power conversions are required and the present power bus operating voltage is suitable for the present power manager configuration, the electronic controller (550) configures the appropriate power converter(s) to make the required power conversion and then connects the power external power devices that need a power conversion to the to the power bus over a power converter (510, 515, 520, 525).

In a further evaluation step the electronic controller processes one or more bus voltage evaluations to determine if there is a more suitable bus voltage for the present power manager configuration and if so, the electronic controller (550) resets the power bus operating voltage to a new operating voltage selected from the list of voltage operating points and reconfigures power converters and reconnects the external power devices to the power bus over the same or different connection paths. The electronic controller (550) periodically polls each device port to refresh system information including the power characteristics of external power devices connected to device ports and repeats the power bus operating voltage evaluation described above as the configuration of the power manager changes due to added or removed power device connections and/or changes in power characteristics of connected devices.

6 EXAMPLES 6.1 Example 1: Operating Mode

The electronic controller (550) has previously set the power bus operating voltage to a desired power bus voltage or to a default bus voltage such as at initial power up. The electronic controller stores a plurality of power bus operating voltage values that it can operate with and also stores power manager performance criteria in a memory associated with the power manager. The electronic controller polls each device port and determines the power characteristics of all of the connected power devices (530, 540) and compares the power characteristics (e.g. operating voltage range) of all of the connected power devices with the present power bus operating voltage value. The electronic controller then uses one or more rules or algorithms stored in the memory module to determine if the present power bus operating voltage value should be maintained or changed to meet one or more of the desired operating criteria. If the present power bus operating voltage value is acceptable and the device configuration has not changed from the last time the electronic controller polled the device ports, no changes in operating parameters of the power manager are carried out. If the present power bus operating voltage value is acceptable and the device configuration has changed from the last time the electronic controller polled the device ports, the electronic controller makes the appropriate operating parameter adjustments such as to connect a power device to the bus with or without a conversion by actuating appropriate switches (not shown) and setting power converter operating points as required to connect power devices to the power bus. However, if the electronic controller determines that a change to the power bus operating voltage will better meet one or more power manager operating criteria defined in the energy management schema, it resets the power bus operating voltage value to one of the voltage values stored in memory and, if needed, makes the appropriate changes to power manager device settings and connections. Such changes include readjusting power converter settings to accommodate the new power bus voltage value, connecting power devices that require power conversion to the bus through one or more power converters, and connecting power devices with power requirements that match the new power bus voltage directly to the power bus without a power conversion.

6.2 Example 2 Algorithm for Minimizing Power Conversion Losses

In one particularly beneficial embodiment, the electronic controller (550) uses the below listed algorithm to minimize power loss due to power conversions when a single power source is connected to the power manager. This algorithm uses the fundamental relationship that power lost in a converter is proportional to the difference between the power converter input and output voltages multiplied by a loss factor. The loss factor is generally power converter dependent and may vary from one power converter type or model to another. Additionally loss factor may depend on input to output current amplitude ratio which can be determined from the input and output voltage and the total power being converted. Accordingly for a given system, loss factor values may comprise a preset value depending on power converter type plus a current ratio estimate based on voltage ratio and total power being converted. Otherwise loss factors for various conditions can be stored in a look up table or estimated in various other ways. Alternately the algorithm can be simplified to only consider the voltage difference across the power converters.

An illustrative, non-limiting example of use of the algorithm follows. In this example, the system includes one input and one output power converter. The algorithm can be expanded to use any number of input and output power converters.

-   1) Detect the operating voltage and current of the power source and     each of the power loads. -   2) Does the power source operating voltage range allow connection     with the power bus at the present power bus operating voltage?     -   a) Yes—Connect the power source to the power bus without         conversion, go to step 3.     -   b) No—Calculate a power bus voltage value that minimizes total         power loss through all converters in the system.     -   i. Let Ls=input conversion loss per Volt difference converted         for a given input voltage and current in the input converter.     -   ii. Let Lo=output conversion loss per Volt difference converted         for a given output voltage and current on the output converter.     -   iii. Let Iin=The Input current to an input power converter.     -   iv. Let Iout=the output current from an output power converter.     -   v. Let Vin=the voltage at an input power converter.     -   vi. Let Vout=the voltage at an output power converter.     -   vii. Select Ls and Lo from a stored table of values based on         Vin, Vout, Iin, and Tout requirements.     -   viii. Select Vbus by minimizing:

Ls*|Vin−Vbus|+Lo*|Vout−Vbus|  Equation 2

-   -   ix. Select a Vbus value stored in memory that most closely         matches the Vbus value calculated in Equation 2.     -   x. Set the input power converter to connect the input source to         the power bus with the power bus voltage value equal to the         selected Vbus value, go to step 3.

-   3) Set output power converter(s) to power any output device(s) from     the power bus at the present power bus voltage value.

Further illustrative, non-limiting, examples include the of use of the algorithm for minimizing power conversion losses expanded to one or more input power conversions and/or one or more output power conversion. When a single input power conversion and multiple output power conversions are required, selecting Vbus includes minimizing the equation:

$\begin{matrix} {\left( {{Ls}*{{{V{in}} - {V{bus}}}}} \right) + {\sum\limits_{y = 1}^{n}\; \left( {{Lo}_{y}*{{{V{out}}_{y} - {V{bus}}_{y}}}} \right)}} & {{Equation}\mspace{14mu} 3} \end{matrix}$

-   -   Where: n=number of output power conversions; and where Lo may         not be the same for each output power converter

Where multiple input power conversions and multiple output power conversions are required, selecting Vbus includes minimizing the equation:

$\begin{matrix} {{\sum\limits_{x = 1}^{m}\; \left( {{Ls}_{x}*{{{V{in}}_{x} - {V{bus}}_{x}}}} \right)} + {\sum\limits_{y = 1}^{n}\left( {{Lo}_{y}*{{{V{out}}_{y} - {V{bus}}_{y}}}} \right)}} & {{Equation}\mspace{14mu} 4} \end{matrix}$

-   -   Where: m=number of input power conversions; and n=number of         output power conversions; where Ls may not be the same for each         input power converter; and where Lo may not be the same for each         output power converter.

6.3 Example 3: Practical Example for Minimizing Conversion Power Loss

As can be seen from examining Equations 1 and 2, the power loss is minimized by minimizing the difference between the input and output power conversion. As an example, referring to FIG. 5, the power manager (500) has a default bus voltage value of 15 volts. A 30 volt power source (530 a) is connected to one of the input ports (503 a) and 30 volt power loads (540 a and 540 b) are connected to each of the two output ports (504 a and 504 b). The output loss, Lo, is the same for each output power conversion. The algorithm described above determines that the input loss is 15 Ls based on the difference Vin−Vbus and that the output loss Lo is 30Lo based on 2×Vout−Vbus (i.e. one loss for each output device). Thus, the simple answer is to make Vbus equal to 30 volts, which allows all three devices to be connected to the power bus without a power conversion. However, the algorithm then checks the lookup table for 30 volts but finds that 28 volts is the closest match and the bus voltage is set to 28 Volts. In the next step, the input power converter (515) is set to convert the 30 volt input source (530 a) to 28 volts for connection to the power bus (505). In step 3, each of the output converters (520) and (525) are set to convert the 28 volt power bus voltage to 30 volts to power the 30 volt power loads (540 a and 540 b). In this case where the bus voltage is set to 28 volts the power loss is 2 Ls on the input side and 4 Lo on the output side. This the power loss is decreased from 15 Ls+30 Lo to 2 Ls+4 Lo.

It will also be recognized by those skilled in the art that, while the invention has been described above in terms of preferred embodiments, it is not limited thereto. Whereas exemplary embodiments include specific characteristics such as, for example, numbers of device ports, certain bus voltages and voltage ranges, power converter ranges, DC-to-DC power conversion, those skilled in the art will recognize that its usefulness is not limited thereto. Various features and aspects of the above described invention may be used individually or jointly. Further, although the invention has been described in the context of its implementation in a particular environment, and for particular applications (e.g. implemented within a power manager), those skilled in the art will recognize that its usefulness is not limited thereto and that the present invention can be beneficially utilized in any number of environments and implementations where it is desirable to selectively connect power devices to a common power bus and to manage power distributing and minimize power losses due to power conversions or other factors related to power parameters of power devices. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the invention as disclosed herein. 

1. A power manager comprising: a power bus operating at with a first substantially constant DC bus voltage operating point; an electronic controller including a memory module; a plurality device ports operably connectable to the power bus wherein at least a portion of the plurality of device ports is interfaced with an external power device; an input power converter having an input side and an output side disposed along an input power converting channel between the power bus and an input device port wherein the input power converter input side connects to the input device port and the input power converter output side connects to the power bus; an output power converter having an input side and an output side disposed along an input power converting channel between the power bus and an output device port wherein the output power converter output side connects to the output device port and the output power converter input side connects to the power bus; and a bus sensor module in communication with the electronic controller configured to sense the DC bus voltage, wherein the power manager is operable to select one or more external power devices to connect to the power bus over one of the input power converter and the output power converter and to calculate a total power conversion loss associated with power converting the selected external power devices based on the first substantially constant DC bus voltage operating point. 2-20. (canceled)
 21. A power manager comprising: a power bus; an electronic controller including a memory module; a plurality device ports operably connected to the power bus; an input power converter connected to the power bus; an output power converter connected to the power bus; and a bus sensor module in communication with the electronic controller configured to sense a DC bus voltage of the power bus, wherein the power manager is operable to select an external power device to connect to the power bus over one of the device ports and to calculate a total power conversion loss associated with power converting the external power device. 